Manila, Philippines -- The award-winning head of a Philippine online news site that has aggressively covered President Rodrigo Duterte's administration was freed on bail Thursday after her arrest in a libel case.

National Bureau of Investigation agents served the warrant against Maria Ressa late Wednesday afternoon and escorted her from the Rappler Inc. office to NBI headquarters, where she stayed overnight in an office. The move against Ressa, who was one of Time magazine's Persons of the Year last year, was denounced by her outfit, Rappler Inc., and media watchdogs as a threat to press freedom. Duterte's government said the arrest was a normal step in response to a criminal complaint.

"What we're seeing is death by a thousand cuts of our democracy," Ressa told reporters after posting bail in the Manila regional trial court that issued a warrant for her arrest.

Ressa spoke out forcefully about the role U.S.-based social media giants, most notably Facebook, which is hugely popular in the Philippines, had in spreading "tainted" information to in a way that she said was distorting the democratic process worldwide.

Rappler CEO Maria Ressa on battling disinformation on social media

"We always say information is power, right? Well, what happens when information is tainted and toxic sludge poisons are introduced into the body of democracy?" she asked.

Ressa said attacks against her and Rappler began appearing on Facebook in the summer of 2016. After a three-part series Rappler published in October of that year, on social media propaganda, she said she was pummeled by an average of 90 hate messages per hour.

"At the beginning, for about two weeks, I was trying to respond. And then I realized they're not looking for an answer, they want to pound me into silence," Ressa told CBSN's Reena Ninan. "That was when I realized this is something new. It's a new weapon against journalists."

The cyber libel claim

Rappler's 2012 article that brought the libel charges included allegations that a businessman was linked to illegal drugs, human trafficking and a murder case, citing an unspecified intelligence report. The story also said a car registered in his name had been used by the country's chief justice, who was later ousted in an impeachment trial.

Wilfredo Keng denied the allegations in a statement and welcomed the justice department's indictment of Ressa and a former Rappler researcher, Reynaldo Santos Jr., adding he was determined to see the legal battle through. He said he has no criminal record.

"Rappler, Ressa and Santos continue to hold themselves high above any accountability to provide credible and justifiable reason for why they continue to harass an ordinary private citizen and businessman despite having absolutely no basis for their claims," Keng said in a statement.

"With one click of a button, they destroyed my reputation and endangered my life," Keng said.

Amnesty International Philippines said Ressa's arrest was based on a "trumped up libel charge."

"This is brazenly politically motivated, and consistent with the authorities' threats and repeated targeting of Ressa and her team," it said.

Justice Secretary Menardo Guevarra said the arrest was "merely part of any criminal procedure." Duterte's spokesman said the charge against Ressa was based on facts which she should simply answer and had "nothing to do" with press freedom.

Rappler is one of several local and international news agencies deemed critical of Duterte's policies.

Duterte had already banned a Rappler reporter from his news briefings after the government's corporate watchdog found that the news site violated a constitutional prohibition on foreign ownership of media when it received money from an international investment firm. Rappler, founded in 2012, rejected the ruling.

In its selection of Ressa as a Person of the Year, Time magazine cited her and several other journalists as "guardians" in what it said was an effort to emphasize the importance of reporters' work in an increasingly hostile world.

Ressa, who has worked with CNN, also last year received a Press Freedom award from the New York-based Committee to Protect Journalists, and the International Center for Journalists' Knight International Journalism Award.